Consumers and retailers have been advised to destroy all Irish pork products bought within the past two months over fears they have been contaminated with a toxic substance.
The action was taken after dioxins were found in slaughtered pigs thought to have eaten contaminated feed.
What are dioxins?
Dioxins are a group of chemicals that can be produced by natural events such as forest fires, but are more commonly formed as by-products of industrial combustion and chemical processes. They also occur as impurities in some products, particularly pesticides. Rhodri Evans, chief toxicology specialist from the Food Safety Authority of Ireland, said these compounds were persistent in the environment and that people were exposed to dioxins in their everyday lives: "If you smoke you are exposed to very low levels of dioxin. The risk is associated with very high levels over a lifetime," he explained.
How dangerous is food contaminated by dioxins?
The UK Food Standards Agency says it does not believe there is "significant risk to UK consumers", because adverse health effects from eating affected products are only likely if people are exposed to relatively high levels of this contaminant for long periods. Nevertheless, it has advised consumers not to eat pork or pork products labelled as being from the Republic of Ireland or Northern Ireland while it continues to investigate whether contaminated products were distributed in the UK.
What effect would it have if you ate contaminated products?
Professor Hugh Pennington, from the University of Aberdeen, said the figures quoted for the amounts of dioxin present in the pork did not seem particularly high. He added: "I think the health effects are probably going to be too small to measure." But there is evidence that dioxins can cause cancer along with other effects on the immune system. In European regulation, dioxins, along with other potentially harmful chemicals called furans and dioxin-like PCBs, are reported as a single value known as the total Toxic Equivalent (TEQ). There are 29 chemicals of concern in this class. The Food Standards Agency says it is awaiting detailed data showing how much of each chemical there is in the contaminated pork.
How can dioxins get into the food chain?
Dioxin contamination of food can occur from two sources. The main source is animal feed contaminated with chemicals. The second is contamination from the environment where animals may be kept. In this particular instance, the contamination is associated with contaminated feed given to the pigs.
How did the dioxins get into this animal feed?
The matter is still under investigation, but the contamination is isolated to one feed producer.
When was the problem discovered?
The Food Safety Authority of Ireland says it was notified of a potential problem last Monday that was confined to the less toxic PCBs [a type of industrial pollutant]. It investigated further and isolated other potentially affected farms. On Saturday afternoon it was confirmed that dioxins were present in Irish pork.
It is known that beef farms are involved - is there a risk beef products have been contaminated?
Mr Evans said that, according to an initial assessment, there was no risk to beef products, but the farms affected have been isolated and further investigations are ongoing to confirm that.